The IMF warning in a preliminary draft of its latest debt sustainability report came as Greece readies for a Sunday referendum on an international bailout deal that Prime Minister Alexis Tsipras has urged voters to reject.
The Washington-based institution, which is part of a "troika" that includes the European Commission and European Central Bank that is overseeing the bailout, said that even if Greek policies came back on track, loans made by Europe "will need to be extended significantly" and that the country would need further concessional financing.
The report was made based on assessments last week, before Greek banks have been closed and the country had defaulted on an IMF repayment.
